For best operational performance of the device, use good printed circuit board (PCB) layout practices, including:
- Noise can propagate into analog circuitry through
the power connections of the board and propagate to the power pins of
the op amp. Bypass capacitors are used to reduce the coupled noise by
providing a low-impedance path to ground.
- Connect low-ESR,
0.1µF ceramic bypass capacitors between each supply pin and
ground, placed as close to the device as possible. A single
bypass capacitor from V+ to ground is adequate for single-supply
applications.
- Separate grounding for analog and digital portions of circuitry is one of the simplest and most effective methods of noise suppression. One or more layers on multilayer PCBs are usually devoted to ground planes. A ground plane helps distribute heat and reduces electromagnetic interference (EMI) noise pickup. Take care to physically separate digital and analog grounds, paying attention to the flow of the ground current. For more detailed information, see Circuit Board Layout Techniques.
- To reduce parasitic coupling, run the input traces as far away from the supply or output traces as possible. If these traces cannot be kept separate, crossing the sensitive trace at a 90 degree angle is much better as opposed to running the traces in parallel with the noisy trace.
- Place the external components as close to the device as possible, as shown in Figure 8-8. Keeping RF and RG close to the inverting input minimizes parasitic capacitance.
- Keep the length of input traces as short as possible. Remember that the input traces are the most sensitive part of the circuit.
- Consider a driven, low-impedance guard ring
around the critical traces. A guard ring can significantly reduce
leakage currents from nearby traces that are at different
potentials.
- Cleaning the PCB following board assembly is recommended for best performance.
- Any precision integrated circuit can experience performance shifts resulting from moisture ingress into the plastic package. Following any aqueous PCB cleaning process, baking the PCB assembly is recommended to remove moisture introduced into the device packaging during the cleaning process. A low-temperature, post-cleaning bake at 85°C for 30 minutes is sufficient for most circumstances.